1. Field of the Invention
The invention relates to an ink cartridge and, more particularly, to an ink cartridge having an improved joint portion.
2. Related Background Art
An ink cartridge of an exchange type which is mounted in an ink jet recording apparatus is mainly classified into the following two types.
According to one type, a fiber member such as a sponge or the like is arranged into a liquid supply port of the ink cartridge, leakage of ink is prevented by the fiber member, and liquid is supplied to a liquid discharge head in a state where the fiber member is come into pressure contact with a liquid introducing port communicating with the liquid discharge head.
According to the other type, a joint member having a slit is arranged in the ink cartridge and the liquid is supplied by inserting a liquid supply needle communicating with the liquid discharge head into the slit.
As a liquid supplying method of the ink jet recording apparatus using the ink cartridge having the joint member according to the latter type, there can be mentioned: a tube supplying method whereby the liquid supply needle is inserted into the slit and in such a state, the liquid is supplied from a liquid enclosing portion to the liquid discharge head via a tube communicating with the liquid supply needle; and an intermittent ink supplying method whereby the liquid supply needle is inserted into the slit each time the ink is supplied, so that the liquid is supplied (hereinafter, an expression “pit-in” is used for convenience of explanation); or the like.
The joint member which is used in the pit-in supplying method is ordinarily fitted into a casing and fixed. A pressure is applied in the clamping direction of the slit by the fitting. As a joint member with such a construction, for example, there has been disclosed a construction in which a slit is formed in a flat elastic member (rubber) and the slit itself is widened by making a projection come into contact with the slit portion, thereby releasing the air for the ink supply.
However, according to the tube supplying method and the pit-in supplying method mentioned above, a problem can occur such that the ink leaks from the joint member.
In the case of the tube supplying method, although the joint member and the liquid supply needle of the ink cartridge are kept connected, there is a case where the clamping pressure applied to the liquid supply needle from the joint member is decreased by creep deformation of the joint member and the ink leaks. There is also a case where when the liquid supply needle is inserted, the joint member is damaged and the ink leaks from a damaged portion.
In the pit-in supplying method, although the number of joining times differs in dependence on a capacity of the ink enclosing portion and that of the sub-tank of the ink jet recording head, since the joining operation is executed about tens to 100 times, there is a case where the joint member deteriorates and the ink leaks.
To prevent the occurrence of such leakage, it is necessary to determine a rubber material, a thickness of rubber, a shape of the projection, a shape of the slit, and the like. An inserting force is necessary when the slit in the elastic member is opened by inserting the projection into the slit so as to be come into contact therewith. When the rubber thickness or the like increases, while the reliability against the ink leakage is generally improved, there is a tendency of an increase in inserting force and it can burden a driving system of the main body.